As HIV-infected individuals continue to age, non-infectious complications increase in frequency. Despite the first descriptions of patient cases in 1987, little is known about the pathogenesis of pulmonary hypertension associated with HIV (PAH-HIV). Chronic exposure to viral products such as HIV-1 Nef and HIV-induced immune deregulation in the lung may contribute to pulmonary vascular disease, particularly through their impact on pulmonary endothelial cells (EC). Our group was the first to associate the HIV-1 nef protein with the pathogenesis of vascular remodeling PAH-HIV. We longitudinally followed 34 individuals with PAH-HIV and collected sequential clinical and echocardiographic; we created and curated a repository of plasma, bronchial lavage fluid and cells. We sequenced the nef gene from blood and lung samples from patients with PAH, elevated pulmonary artery systolic pressures and from non- PAH HIV infected. We found amino acid substitutions in the Nef protein statistically associated with the PAH phenotype; these substitutions clustered around Nef functional domains that potentially interfere with Nef adaptor functions. Further studies, which are preliminarily reported in this application, suggest that particular amino acid signatures predominate in the lungs compared with the periphery. The lung may be a protected environment that allows the virus to evade immune responses; furthermore, particular nef alleles will enhance T cell responses and result in pulmonary vascular endothelial cell proliferation/apoptosis, disrupt signal transduction pathways and result in vascular remodeling. We hypothesize that allelic variants of nef will have an impact on T cell and pulmonary endothelial cell function. We propose to 1) infect T cells with molecularly cloned virions containing primary nef alleles and measure T cell receptor density; 2) human pulmonary artery endothelial cells will be co-cultured with infected T cells or transfected with nef molecular clone and endothelial cell gene expression, apoptosis and proliferation measured and 3) determine whether the lung is a protected compartment for evolution of nef sequences. These studies will examine the functional properties of nef alleles containing these amino acid substitutions from PAH-HIV individuals. The studies proposed in this application will use existing biospecimens and cloned nef alleles to examine the mechanisms whereby HIV-nef influences pulmonary vascular remodeling in the pathogenesis of PAH-HIV. Our research tem, with a combination of basic and clinician scientists is well poised to address how the nef viral protein and immune dysregulation are contributing factors to this lung complication of HIV.